The invention relates to a bone shaping system made up of an instrument holder and a surgical instrument, i.e., a surgical tool head, for attachment to the holder. The holder includes a shank equipped with a head designed to receive an instrument, and an annular locking component mounted so as to slide about the shank, under the head, equipped with locking means which cooperate with the head so as to lock the instrument on the head, and pushed against the head by a helical spring. The present surgical tool head is disposed to mate with and attach to the head of the tool holder. An example of a tool holder suitable for practice with the present invention is disclosed in U.S. Patent Application Publication No. 2005/0251145, the content of which is incorporated herein by reference.
One such system is described in European Patent 0782840, the content of which is incorporated herein by reference thereto, and includes a shaft (10), equipped at one end with a cutting head holder (12) which has a bayonet joint and lock. A hemispherical or conical rotary cutting head (1) has inner radial rods (4) to engage with the bayonet joint. The cutting head contains an axial guide tube (5) between the inner ends of the radial rods and a central aperture (3) to receive a twist drill (9) which makes a hole in the middle of the recess formed by the cutting head. The lower end of the guide tube has one or more notches to receive corresponding studs on the twist drill so they rotate together. Other systems provide for reshaping of the bone, but the tool itself generally obstructs the view of the bone lobe during cutting.
A total hip replacement procedure removes the organic stem of a bulbous bone joint replacing it with an artificial one. This is a relatively radical surgical procedure, and alternative processes exist that attempt to preserve the natural joint. One such procedure places a hard, external prosthetic cap over a resurfaced bulbous bone joint. The cap has an external spherical surface which mates with a hip socket. The cap is often made of metal and has precise interface dimensions which must be matched to the bone of the joint in order for the cap to properly fit over the joint, and to properly function in its corresponding prosthetic hip socket. Therefore, there is a need for cutters capable of cutting and shaping the bulbous bone joint in preparation for the reception of a prosthetic cap. Such an application presents other challenges in guidance and control, particularly, that of ensuring that the stem of the bulbous bone joint is not damaged in the process. Still further, what is needed therefore is a system which enables controlled cutting and reshaping of the bulbous bone joint in preparation for the reception of a bone cap prosthesis. In particular, what is needed is a reamer capable of cutting the bulbous bone joint to closely receive a bulbous bone joint prosthetic cap.